Laser Printer

Overview

A monochrome laser printer reproduces a page by electrostatics rather than ink. A laser paints an invisible charge pattern on a rotating photoconductive drum; toner powder clings to that pattern, transfers to paper, and is melted permanently into the fibers by heat and pressure. The result is fast, sharp, smudge-proof text at low cost per page.

Every module mounts in the sheet-metal Chassis & Covers. The Laser Scanner Unit writes the image, the Drum Unit holds it, and the Toner Cartridge supplies powder. The Transfer Unit moves toner onto paper and the Fuser Unit bonds it, while the Paper Path feeds sheets and the Main Controller Board rasterizes incoming jobs.

How it works

The print cycle is electrophotography in six steps. The drum surface is first uniformly charged. The laser scanner sweeps a modulated beam across the spinning drum through a rotating polygon mirror, discharging the spots that will print and writing a latent electrostatic image. Charged toner from the cartridge develops that image, adhering only to the discharged areas.

As paper advances along the path, the transfer unit applies an opposite charge from behind the sheet, pulling the toner off the drum onto the page. The sheet then enters the Fuser Unit, where a heated roller near 180 °C and a pressure roller melt the toner into the paper. The Drive Train gears synchronize drum, rollers, and fuser, the Engine Control Board sequences the high-voltage and motor timing, and the Control Panel reports status to the operator.